The invention relates generally to pressure sensors, and more particularly to pressure sensors for measuring pressures at high temperatures.
Pressure sensors are used in a wide range of industrial and consumer applications. Pressures of many different magnitudes may be measured using various types of pressure sensors, such as Bourdon-tube type pressure sensors, diaphragm-based pressure sensors, and piezoresistive pressure sensors on silicon or silicon on insulator (SOI). Several variations of the diaphragm-based pressure sensor have been utilized to measure different ranges of pressure, such as by utilizing cantilever-based pressure sensors, optically read pressure sensors and the like.
Some known pressure sensors have been formed using semiconductor materials, and the like, which may be grown on foreign substrates or support layers to form a laminate. A support layer may include, for example, sapphire (aluminum oxide), which may be used because of inherent physical and chemical properties of the aluminum oxide. An example of a suitable semiconductor material is gallium nitride (GaN). Referring specifically to FIG. 1, one known pressure sensor 10 includes silicon material 16 deposited on a substrate 18. A semiconductor material 14 which exhibits piezo-like characteristics when introduced to a force is deposited on the silicon material 16, and is capped with a silicon dioxide layer 12. Optional metallic or ohmic contacts 20, 22 are included. An air gap 26 is defined within the silicon material 16. The change in the thickness 24 of the air gap 26, due to the force upon the semiconductor material 14, is measured and that change is equated with a pressure change.
Another known pressure sensor 30, with specific reference to FIG. 2, includes a semiconductor material 34 having piezo-like characteristics when introduced to a force is deposited on the silicon material 36. The semiconductor material 34 is capped with a silicon dioxide layer 32, and metallic or ohmic contacts 38, 40 are included. A force on the semiconductor material 34 causes the semiconductor material 34 to flex, thereby creating a change in the electrical state of the semiconductor material 34. A circuit between the metallic or ohmic contacts 38, 40 reads the change in resistance due to the flexing of the semiconductor material 34 and converts such change into a pressure change.